The present invention relates to an internal combustion engine, in particular for a vehicle, having a split cooling system, and to a vehicle having such an internal combustion engine.
In particular, internal combustion engines are known which have one cylinder, or usually have a plurality of cylinders, with pistons by way of which a crankshaft is driven, with the result that the internal combustion engine constitutes a combustion engine. Such internal combustion engines usually have what is referred to as a crank casing in which the crankshaft is mounted and in which the cylinders are at least partially formed, and a cylinder head which closes off the cylinders on one end side.
In order to cool internal combustion engines, it is also known to use cooling circuits which run through them and in which the heat which is generated in the internal combustion engine is at least partially discharged by way of a coolant which circulates in the cooling circuit. The coolant can be, in particular, water. The coolant is often also provided with additives such as, for example, an antifreeze agent.
Against this background, it is also known from the prior art to split the cooling circuit through an internal combustion engine, in particular through a combustion engine, into a plurality of secondary circuits, with the result that the flow of the coolant splits at at least one branching point into two or more separate coolant flows which serve to cool different parts of the internal combustion engine. This is often also referred to as a split cooling system.
Such an internal combustion engine with a split cooling system is described in German laid-open patent application DE 102012200527 A1. This internal combustion engine has, in one crank casing, at least three cylinders arranged in a row, a cylinder head with an inlet side and an outlet side and in each case one web region between the cylinders. In this context, a first and a second coolant duct, arranged largely parallel to a longitudinal axis of the internal combustion engine, for a coolant are provided for the cylinder head and/or the crank casing. The first and second coolant ducts are connected to each other in a coolant-conducting fashion through at least one web-drilled hole. The coolant flow in the first coolant duct is split at a plurality of branching points into partial cooling circuits which run parallel to one another and are combined again in the second coolant duct. In this context, a flow cross-section of the first coolant duct in the direction of flow of the coolant is smaller, and a flow cross-section of the second coolant duct in the direction of flow of the coolant is larger, as a result of which essentially uniformly efficient cooling and therefore distribution of temperature in the internal combustion engine along its longitudinal axis can be achieved.
A further combustion engine with an engine block and a cylinder head as well as with a split cooling system is described in patent document U.S. Pat. No. 5,337,704. The cooling system has a first cooling duct which is formed in the cylinder head and which is adjoined by a coolant line with a branching junction which splits the cooling system into two cooling branches. One of these two cooling branches leads into a second cooling duct which is formed in the engine block. A thermostat which opens only above a specific temperature threshold and permits a flow of coolant into the second cooling duct is provided at the branching point. In contrast, the thermostat closes below the temperature threshold and prevents a flow of coolant into the second cooling duct through the engine block. Therefore, during a heating phase the cooling is limited to the cylinder head, while afterward, from the time when the temperature threshold is exceeded, there is also a flow of coolant through the engine block, which is therefore cooled.
In these combustion engines which are known from the prior art, the coolant flows which occur during operation when warming up and afterward are predefined by the geometry and dimensioning of the corresponding cooling ducts which are already defined when the respective combustion engine is manufactured.
Against this background, the invention is based on the object of making available an internal combustion engine with a cooling system which is improved in comparison therewith.
This and other objects are achieved by an internal combustion engine according to embodiments of the invention and/or by a vehicle including such an internal combustion engine according to embodiments of the invention.
A first aspect of the invention relates to an internal combustion engine, in particular for a vehicle. The internal combustion engine has a crank casing, a cylinder head, a coolant feedline, a cooling duct branching junction, a first coolant duct which runs at least partially through the cylinder head, and a second coolant duct which runs at least partially through the crank casing. In this context, the coolant feedline is connected to the cooling duct branching junction in order to feed in a coolant, and the first coolant duct and the second coolant duct are each connected to the cooling duct branching junction in order to be supplied with the coolant by the latter. Provided at the cooling duct branching junction is a temperature-sensitive flow regulating device which is configured to variably set, over a range and as a function of the temperature, the ratio of the coolant volumetric flow from the cooling duct branching junction into the first coolant duct with respect to the coolant volumetric flow from the cooling duct branching junction into the second coolant duct.
The term “internal combustion engine” is to be understood in the sense of the invention as a combustion engine which converts chemical energy into mechanical work. In particular, spark-ignition engines and diesel engines are internal combustion engines within the sense of the invention, without being restricted thereto.
The term “vehicle” in the sense of the invention is to be understood as meaning any type of land vehicle which is driven by machine force. In particular, non-track-bound motor vehicles such as, for example, passenger cars (PKW), trucks (LKW), motorbikes or buses are respectively vehicles in the sense of the invention.
The term “crank casing” in the sense of the invention is to be understood as being a part of an internal combustion engine in which its cylinders are (at least partially) formed and which has the crankshaft bearing. The term “engine block” is often also used for a crank casing.
The term “cylinder head” in the sense of the invention is to be understood as being a further part of an internal combustion engine which closes off the combustion space of the internal combustion engine with respect to the crank casing. In particular, the cylinder head can also accommodate inlet ducts and outlet ducts and the valve control for the gas exchange processes, oil ducts for lubrication of the valve drive, and also coolant ducts in coolant-cooled engines, the spark plugs in spark-ignition engines, the injection valves in direct-injection spark ignition engines, or the injection nozzles and the glow plugs in diesel engines.
The term “cooling duct branching junction” in the sense of the invention is to be understood as a branching off of a coolant line, similarly to a fork junction or a switching point, into two or more different cooling ducts or cooling branches.
The term “flow regulating device” in the sense of the invention is to be understood as meaning an actuator device which can set the flow of a fluid medium, in particular of coolant, as a variable to be closed-loop or open-loop controlled, over an open-loop or closed-loop control range as a function of at least one manipulated variable. The manipulated variable can be, in particular, a temperature, in particular that of the medium, that of the flow regulating device itself or that of its surroundings. Correspondingly, the meaning of the term “regulate” extends here both to a “closed-loop control” as well as to “open-loop control” in the known sense of open-loop and closed-loop control technology. The medium can be, in particular, a medium which is liquid at the temperatures occurring during regular operation of the internal combustion engine. For example, said medium is composed essentially of water to which it is also possible to add additives, for example an antifreeze agent. Gaseous media are also possible, such as for example in the case of air cooling.
In the sense of the invention, the term “temperature-dependent” is to be understood as meaning, in particular, a dependence on the temperature of the coolant, of the flow regulating device or of its immediate surroundings, or of the cylinder head or of the crank casing.
In the sense of the invention, the term “coolant volumetric flow” or for short “coolant flow” is to be understood as meaning the fluid flow of a coolant, i.e., the directed movement of the coolant, in particular in a coolant duct. The strength of the coolant volumetric flow corresponds to the volume of coolant which flows through a defined cross-section, in particular, that of a coolant duct, per unit of time.
In the sense of the invention, the term “configured” is to be understood as meaning that the corresponding device is already configured or is settable—i.e., configurable—to perform a specific function. The configuration can take place here, for example, by correspondingly setting parameters of a process sequence or of switches or the like in order to activate or deactivate functionalities or settings.
It is therefore possible to use the flow regulating device to variably set the splitting of a coolant flow, fed through the coolant feedline, at the cooling duct branching junction, as a function of the temperature, with the result that different ratios between the coolant volume flows into the various cooling branches are produced as a result thereof. However, in contrast to the known combustion engines described above, this ratio can be set variably and is not restricted to merely connecting or disconnecting the coolant flow into the coolant duct which runs through the crank casing. This permits the cooling of the cylinder head and crank casing to be set in an improved way, in particular in a way which is adapted more precisely to the actual temperature conditions at the internal combustion engine. It is therefore possible, in particular during the warming up of the internal combustion engine, to achieve cooling which is adapted continuously or at least in multiple stages to the actual temperature profile, and therefore to bring about an improvement in the reduction in friction in the internal combustion engine and therefore also to bring about an improvement in the fuel consumption.
Preferred embodiments of the internal combustion engine and developments thereof which, unless specifically excluded, can be randomly combined with one another and with the second aspect of the invention described below, are described in the following.
According to a first preferred embodiment, the flow regulating device is configured to regulate the ratio of the coolant volumetric flows into the first coolant duct and the second coolant duct in such a way that as the temperature rises, the ratio decreases to a minimum value. In this way, at a low temperature the coolant volumetric flow is increasingly directed into the first coolant duct through the cylinder head, while the crank casing is cooled only to relatively small extent by way of a coolant volumetric flow through the second coolant duct. If the temperature rises over time as a manipulated variable of the flow regulating device, this shifts the ratio of the coolant volumetric flows over a range in favor of the second coolant duct, with the result that the crank casing which has then already been heated is then also increasingly cooled, in order to counteract overheating of said crank casing. The minimum value is preferably between 2:1 and 8:1, particularly preferably between 3:1 and 5:1.
According to preferred developments of this embodiment, the flow regulating device is configured to regulate the ratio in such a way that as the temperature of the flow regulating device rises, the decrease in the ratio takes place continuously, in a plurality of essentially discrete steps, or according to a combination of the two. In this way, the granularity for the setting of the coolant volumetric flow ratio can be adapted to the requirements of the internal combustion engine.
According to a further preferred embodiment, the flow regulating device has a thermostatic valve. This may be, in particular, a material-based thermostatic valve which regulates the coolant flow at the cooling duct branching junction as a function of the thermally induced volume expansion of a material, in particular of a wax, over a regulating range. This permits easy setting of the ratio of the coolant volumetric flows by way of a single component, i.e., the thermostatic valve.
According to a further preferred embodiment, the flow regulating device is configured in such a way that when a specific pressure threshold is exceeded in the second coolant duct, the ratio decreases. In this way, it is also possible to trigger a reduction in the ratio solely or essentially by an overpressure with respect to the pressure threshold, independently of the temperature-induced change in said ratio. A relevant application case could, in particular, take the form of avoiding overheating of the crank casing, in particular in the region of the cylinders, if the internal combustion engine is already very highly loaded during the warming up, while it has not yet entirely reached its operational temperature. This may be the case, for example, in the case of high rotational speeds when still cold such as can occur, in particular, in the cold time of year or in the case of driving at a high speed (e.g., highway driving) without an appreciable warming up phase and with a relatively low load.
According to one preferred development of this embodiment, the flow regulating device is mounted in the cooling duct branching junction by way of a spring whose spring force is selected such that when the pressure applied to the flow regulating device from the second coolant duct exceeds the pressure threshold, the spring is deflected in such a way that at least part of the flow regulating device is moved by virtue of the fact that the ratio decreases. In this way, a purely passive overpressure regulating device or mechanism can be made available which, in particular, requires no additional pressure sensors or control devices and can therefore be implemented economically in terms of space and costs and with low complexity and a high level of robustness.
According to a further preferred embodiment, the flow regulating device can be operated autonomously, in particular independently of an electrical power supply or actuation device. In this way, external feedlines or communication connections for supplying energy and/or actuation device can be dispensed with, which can in turn contribute to implementation which is favorable in terms of space and costs and has a low complexity and easy replaceability. The temperature detection is then carried out directly by the flow regulating device. The above-mentioned material-based thermostatic valve can be embodied without an external electrical power supply and without an actuation device, in order thereby to provide a possible device or mechanism of implementing such an autonomous flow regulating device.
According to an alternative embodiment to this, the flow regulating device can be actuated externally by way of a signal, wherein the signal causes the flow regulating device to change the ratio or to set it to a specific value or to assume a specific setting for this purpose. The actuation device can, in particular, also be a regulating device or can be controlled with the characteristic curve.
According to a further preferred embodiment, the flow regulating device has a heating element with which the flow regulating device can be heated. In this way, the flow regulating device can also be brought to a desired operating temperature independently of its heating by the coolant flow in the cooling duct branching junction. This can serve, in particular, to pre-heat the flow regulating device briefly after the internal combustion engine starts, with the result that the temperature of said internal combustion engine is somewhat in advance of the coolant temperature. In this way, the thermal-capacity-induced inertia during the heating of the flow regulating device can be countered by the coolant. This can additionally contribute to avoiding overheating of the crank casing, in particular in the region of the cylinder, since the pre-heated flow regulating device can react with only a short delay to an increase in temperature of the coolant to a temperature range at which a reduction of the ratio is to take place. According to one preferred development, the heating element can also be used in conjunction with the embodiment described above in order to be actuated or regulated by way of a signal and thereby set, in particular as a function of characteristic curves, the setting of the flow regulating device and therefore the ratio of the cooling flows.
According to a further preferred embodiment, the flow regulating device has a first component and a second component which are coupled, so as to be movable with respect to each other, by way of an expansion element which expands as a function of the temperature. The second component is directly or indirectly supported on a wall of the internal combustion engine. The flow regulating device is configured and arranged here in such a way that the first component at least partially closes a connecting region from the coolant feedline to the second coolant duct at a temperature of the expansion element below a specific temperature threshold. Further, the flow regulating device is configured in such a way that when there is a rise in temperature of the expansion element to a temperature above the temperature threshold, the second component is shifted relative to the first component, owing to the expansion of the expansion element caused by the rise in temperature, in such a way that said first component is as a result moved at least partially out of the connecting region. In this way, an effective and also autonomous mechanical implementation of the flow regulating device is made possible. The above-mentioned heating element can optionally also be added, and the above-mentioned overpressure protection is possible in this embodiment.
In one preferred development of this embodiment, provided in the internal combustion engine is an enclosed cavity which is closed by the first component and into which said first component is at least partially moved when the expansion element expands. In this way, on the one hand a movability of the first component, which is necessary for functional reasons, is realized in a structurally simple fashion and, on the other hand, if the cavity is filled with a compressible medium, in particular air, said cavity can also serve as an additional suspension which applies to the first component a force which is opposed to the movement of said first component, and therefore assists the return movement thereof when said first component is to be moved again in the direction of the connecting region, in particular in the case of a reduction in temperature or pressure.
According to a further preferred embodiment, the internal combustion engine also has a coolant pump, wherein the coolant delivery capacity of the coolant pump is regulated as a function of the temperature, in particular as a function of the coolant temperature at the coolant pump or at the location of a temperature sensor on the cooling system, in such a way that its delivery rate increases at least in certain sections when the temperature rises. In this way, the variation of the ratio of the coolant volumetric flows can be combined with a variation of the overall available coolant volumetric flow through the coolant feedline. In this way, it is possible, for example in the cold state of the internal combustion engine when a high degree of cooling is not necessary for the cylinder head or for the crank casing, to reduce the power of the pump, and therefore the coolant volumetric flow in the coolant feedline in order to save energy, and at the same an optimized ratio of the coolant volumetric flows can be set by way of the flow regulating device. If the temperature of the internal combustion engine then rises, in addition to changing the ratio of the coolant volumetric flows into the first and second coolant ducts, it is also possible to increase the overall coolant volumetric flow in the coolant feedline, in order thereby to make available the higher overall cooling performance which is then necessary.
According to a further preferred embodiment, the flow regulating device is arranged at least partially in a cavity which is formed in the crank casing or in the cylinder head or in both together. In particular, the cavity can already be formed as a cutout during the manufacture of the internal combustion engine, in particular by casting. However, in addition it is also possible for the cavity to be embodied in the form of a drilled hole in the cylinder head or the crank casing or both. The arrangement of the flow regulating device in such a cavity permits a compact design of the internal combustion engine and in-situ positioning of the flow regulating device at the cooling duct branching junction if the latter is itself embodied as a cavity in the cylinder head, in the crank casing or in both together.
According to preferred variants of this embodiment, the cavity is defined at least partially by a drilled hole or cutout which extends from an outer surface of the crank casing or of the cylinder head into said crank casing or cylinder head. This facilitates the mounting of the flow regulating device since the latter can also be inserted subsequently into the internal combustion engine, in particular if the cylinder head and crank casing are already connected.
According to a further preferred embodiment, at least two of the following elements of the internal combustion engine are embodied in an integral fashion; the coolant feedline, the cooling duct branching junction, the first coolant duct, and the second coolant duct. This can be achieved, in particular, by virtue of the fact that the integrally embodied elements are embodied as a cavity in the crank casing or in the cylinder head or both together. In this way, transitions between the elements can be dispensed with, as a result of which the fabrication complexity and the susceptibility to leaks can be reduced or avoided.
According to a further preferred embodiment, the internal combustion engine has a plurality of cylinders which are grouped into a multiplicity of cylinder banks. A coolant feedline, a cooling duct branching junction, a first coolant duct which runs at least partially through the cylinder head in the region of the respective cylinder bank, and a second coolant duct which runs at least partially through the crank casing in the region of the respective cylinder bank are provided for each of at least two of the cylinder banks. The respective coolant feedline is connected to the respective cooling duct branching junction in order to feed in a coolant, and the respective first coolant duct and the respective second coolant duct are connected to the respective cooling duct branching junction in order to be supplied with the coolant from the latter. In this context, provided at the respective cooling duct branching junction is a temperature-sensitive flow regulating device which is configured to regulate, as a function of the temperature, the ratio of the coolant volumetric flow from the cooling duct branching junction into the respective first coolant duct with respect to the coolant volumetric flow from the respective cooling duct branching junction into the respective second coolant duct. In this way, not only is it possible to carry out splitting of the coolant circuit of the internal combustion engine with respect to a first cooling duct through the cylinder head and to a second duct through the crank casing, it is also possible to make available a plurality of such split partial circuits which cool various cylinder banks of the internal combustion engine. The variable setting of the cooling ratio between the cylinder head and crank casing can therefore be combined with splitting of the total coolant volumetric flow in the cooling system at various cylinder banks of the internal combustion engine, and the desired cooling effect can therefore be made available uniformly even when there are a plurality of cylinder banks.
A second aspect of the invention relates to a vehicle, in particular a motor vehicle, having an internal combustion engine according to the first aspect of the invention, in particular according to any of its above-mentioned embodiments and developments.
What has been respectively stated above with respect to the internal combustion engine also applies equally to the vehicle with such an internal combustion engine.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.